If the brain starts to swell after a stroke, surgery is often the only treatment option – one in which the physicians open the patient’s cranial vault. Up to now, they would reach for the drill and the saw. Soon, a laser beam will cut the bone and lower the risk. A stroke strikes suddenly, and if the infarction is a major one, this may cause the brain to swell. The pressure in the cranial cavity increases, perfusion to the brain diminishes and the brain suffers further damage. To protect it from contusions, the surgeon will often open the patient’s cranial vault – this is referred to as a release craniotomy. Until now, surgeons cut the cranial bones mechanically, that is, with a trephine. However, that approach comes with a truly high risk to the patient: By using the trephine, the surgeon could inadvertently injure the meninges, which could then lead to meningitis and, in the worst case scenario, to death.